Clearly there had to be some kind of bond between them: something that still endured, despite the fallings out and the fear Martha evidently felt towards her stepsister. Or perhaps Mary needed her somehow: if she had spared Martha for a purpose, it might prove crucial if he could work out what that purpose was.

Raven got to his feet.

‘Miss Dempster, thank you for your time and your hospitality, but I must get back to Queen Street. Before I go, I would like to stress that it is imperative I speak to your sister, and soon.’

From her face he could tell she had inferred much from the seriousness of his tone.

‘Do you fear for her, Doctor? Are you quite sure my sister is not in danger from this ailment?’

Raven had to think carefully about how much he could say without putting her in danger. Mary had spared Martha thus far, but that did not guarantee the latter’s safety if Mary felt her sister had betrayed her or become a threat. Equally, he did not wish Mary to know just how much he and Sarah had uncovered. He had already alerted her to their investigation by leaving his card.

‘Do you truly have no notion where she is, or is it perhaps that you do not wish to say?’

She looked worried, as Sarah had observed: uncertain of what she was permitted to reveal.

‘She left in a hurry. She told me little.’

Little wasn’t nothing.

‘If you hear from her, or you learn where I might find her, please do not delay in contacting me.’

Martha put a hand on his arm.

‘What are you not telling me, Dr Raven?’

He looked her in the eye, trying to gauge what might be hidden behind her fearful face. He could see how she was torn between loyalty to Mary and troubling doubts about what her sister might be keeping from her.

‘I could ask you the same question.’

She withdrew the hand, folding her arms about herself.

‘I do not know what you mean,’ she replied.

‘When first we visited, my associate Mrs Banks thought you seemed afraid of your sister.’

Martha looked meekly at floor.

‘I am not,’ she said, her voice quieter.

Raven stepped through the front door then turned to face her one last time.

‘You should be.’

FIFTY-FIVE

aven walked through the open door into Dr Simpson’s study, where he had been summoned. The professor had just returned from a trip to London and Jarvis was remonstrating with him about various items missing from his luggage.

‘Several woollen vests have disappeared: lost or misplaced, presumably,’ the butler was saying as Raven entered the room.

‘They’re not lost,’ Simpson countered, as if this should be obvious. ‘I’ve got them all on.’ He turned to Raven. ‘Train carriages are ferociously cold this time of year.’

Jarvis left the room muttering and shaking his head.